1. Field of the Invention
The present invention relates to a method of processing elongated tubular material, more particularly--but not exclusively--a method of everting sausage casings or packing casings, having been subjected to a surface treatment, wherein the material is passed through a guide member having an annular cross-section and is folded back over the guide member, whilst the material within said guide member is during the everting action displaced into a direction contrary to that of the material outside said guide member.
2. Description of the Prior Art
A method of this kind is disclosed in U.S. Pat. No. 4,075,737 issued on Feb. 28, 1978 to Alfred D. Story. In the respective method tubular material is first passed from a roller through a stationary annular member, subsequently through a displaceable annular member and then folded back over the latter in order to further attach the portion of the tubular material passing both annular members, to the stationary annular member. The displaceable annular member covered by the tubular material is magnetically supported by a carriage which is driven by a motor, said carriage running along an elongated rail. In the case that the annular member is drawn along by the carriage, the end of the tubular material disposed upon a supply reel will simultaneously with the displaceable annular member, be drawn along, said curved end sliding about the latter member and remaining about the same in the space underneath the rail.
Obviously the path of travel of said displaceable annular member is dependent upon the total length of the tubular material upon the supply reel. From this it follows that an entire everting operation can only be performed when the path of travel of the displaceable annular member amounts to at least half the total length of the tubular material upon the supply reel; if, for example, 500 m of tubular material is disposed upon said supply reel, the length of the path of travel of the annular member and thus of the rail has to amount to approximately 250 m.
In actual practice this entails that the supply of the tubular material is stopped as soon as a given length of said material has been everted and the end of the material fastened to the stationary annular member, is fastened upon a core in order to appropriately form said everted material to a package by a reeling action. After having formed the second package of tubular material a subsequent portion of said material has to be passed through the two annular members, folded back around the displaceable annular member and fastened again to the stationary annular member.
The difficulties with the above described method and device are that the friction exerted by the sagging walls of the tubular material which pass each other during the everting operation, will become too intense, even when the actual space available for the path of travel of the carriage with the magnetic support for the displaceable annular member is sufficiently large. This could result in damages to the respective walls of the tubular material. Furthermore the everting action is performed intermittently, as a new front end of tubular material has always to be passed through the two annular members, to be folded back around the displaceable annular member and fastened to the stationary annular member, which is rather time-consuming.
In actual practice elongated tubular material, more particularly sausage casings, should be everted in the case that the outer side of said tubular material to be provided with a coating should subsequently be accomodated inside the tubular material. More particularly, an everting action is desirable in the case that the tubular material consists of cellulose fibers. Said tubular material is in most cases everted by means of pressurized air or by means of a vacuum, a bound off end portion of said material disposed upon a ring, being subjected to a pressure, the remaining portion of the tubular material then being pressed through said ring towards the outside.
It should be noted that a process of everting sausage casings while using a creased and compressed package of tubular material, is disclosed in Netherlands Patent Application No. 77, 14276 filed by the UNION CARBIDE CORPORATION in December, 1976 corresponding to U.S. Pat. No. 4,162,557 (Rasmussen). Said patent application describes that tubular material arriving from a supply reel, is provided with an internal coating and is subsequently tucked upon a mandrel while creasing the tubular material. The package of tubular material so obtained is subsequently disposed upon another mandrel, one end of said package having previously been drawn through the internal space in said package, and fastened upon a coiling core. The package of tubular material enclosed upon the mandrel is subsequently everted by coiling the returned portion of said tubular material, the material then being removed from the everted end upon the coiling device.
Although said method requires a device which occupies little space, the difficulty with the respective invention is that the creased package of tubular material has to be removed from one mandrel and disposed upon the other mandrel prior to the everting action. Though one and the same mandrel could be used for everting and forming the package of tubular material, said known device presents an additional disadvantage in that friction arises in the stationary inner tops of the creases in the package, which implies that said tops are subjected to an intensive wearing off, resulting in that not only the coating but also the tubular material itself will wear away.